Determining mechanical properties of thin films from the loading curve of nanoindentation testing

Nanoindentation has been widely used to evaluate material properties. In this study, we propose a method that utilizes only the loading curves of an indentation test to extract the elastoplastic properties of an elastic-perfectly plastic thin film as well as the plastic properties of a work hardening thin film. The use of loading curve circumvents some common difficulties encountered during the post-processing of experimental unloading curves. Measurements are taken at two different indentation depths, which have different levels of substrate effects and lead to the establishment of independent equations that correlate the material properties with indentation responses. Effective reverse analysis algorithms are proposed by following which the desired film properties can be determined from a sharp indentation test. The extracted material properties agree well with that measured from a bulge test.